JPS63276023A - Projection type liquid crystal display device - Google Patents

Abstract

PURPOSE:To improve a contrast and a write speed by providing a means for making a temperature different between two pieces of glass substrates for constituting a liquid crystal element. CONSTITUTION:The titled device consists of a structure which inserts a liquid crystal 6 between two pieces of glass substrates 2, 8 of each different heat capacity, and on the glass substrate 2, a light absorbing film 3 of chromium and chromium oxide, and a liquid crystal oriented film 5 of an organic substance and SiO are provided. On the other hand, on the glass substrate 8 of a projected light side, the liquid crystal oriented film 5 of the organic substance and SiO, and a transparent electrode 7 of In2O3 are provided. The heat capacity of the glass substrate 8 of the projection side is larger by about 10 times than that of the glass substrate 2 of the laser light side, and also, the film thickness of a light reflecting film 4 of Al provided on the laser light absorbing film 3 is set to 400Angstrom , by which energy of a projected light is absorbed by the laser light absorbing film 3, and a temperature is made different between the glass substrate 2 of the laser light side and the glass substrate 8 of the projected light side. In such a way, the write time is shortened, and also, a write state that the light scattering property is strong is obtained, and the contrast is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a projection type display device using a liquid crystal, and particularly to a liquid crystal element suitable for a device using a low-output semiconductor laser.

[Conventional technology]

Liquid crystal display elements in projection type display devices using conventional liquid crystals are described in the Technical Report of the Television Society (1986).
Discussed in January, 0PT216, PPI~6). However, special consideration must be given to actively absorbing the projected light with a light-absorbing film that absorbs laser light, increasing the haze of the glass substrate on which the light-absorbing film is provided, and increasing the temperature gradient with the opposing glass substrate. It wasn't.

FIG. 2 is an explanatory diagram showing a liquid crystal element in a conventional projection type liquid crystal display device using smectic liquid crystal. As shown in the figure, the structure is such that a liquid crystal 17 is sandwiched between two glass substrates 11°19. On the glass substrate on the laser beam incident side, there are a heat insulating layer 12 made of polyimide, a laser light absorption film 13 made of vanadium oxide phthalocyanine, a light reflection film/electrode made of chromium and aluminum, a liquid crystal block film 15 of 4.5 iOz, and a liquid crystal alignment film 16 made of SiO. It is provided. On the other hand, a liquid crystal alignment film 16 of SiO and a transparent electrode film 18 of ITO are provided on the glass substrate on the projection light side. Both of these glass substrates 11.
On the outside of 19, there is an anti-reflection film 10 that suppresses reflection of incident light.
20 have been applied.

The wavelength of the semiconductor laser used here is 830 nm.
, a halogen lamp is used as the projection light source.

The reason why the heat insulating layer 12 is provided in this structure of the liquid crystal element is to efficiently propagate the heat generated in the laser light absorption film to the liquid crystal 17. This is because the laser light absorption film 13 is in contact with the glass substrate 11 as shown in the figure, so the heat generated in the laser light absorption film 13 flows out to the glass substrate 11 more than it propagates to the liquid crystal 17. This is due to poor thermal efficiency.

Therefore, in order to prevent heat from flowing to the glass substrate 11, the structure was such that a heat insulator Wj12 was provided.

However, with such a structure of a liquid crystal element, the film formation process becomes complicated, and until the laser beam irradiation, there is a gap between the glass substrate 11 on which the light absorption film is provided and the glass substrate 19 on which the transparent electrode film is provided. There is no temperature gradient. For this reason, a relatively large amount of light is required, and
Glass substrate 11 on the light absorption film side and glass substrate 19 on the transparent electrode side
Since there is no temperature gradient between them, a writing state with weak light scattering occurs, resulting in a displayed image with low contrast.

In addition, forming a light-absorbing film or a light-reflecting film on a thin film made of an organic agent such as polyimide complicates the film formation process, and there are problems with the process and the relationship between the expansion coefficients of organic thin films and metal films. There are many problems such as cracks occurring.

[Problem that the invention seeks to solve]

The above-mentioned conventional technology does not take into account the structure of a liquid crystal element that forms a written state with strong light scattering property at a high speed using a semiconductor laser beam of low power, and has the problem of low contrast and writing speed.

The purpose of the invention is to improve contrast and writing speed.

[Means for solving problems]

The above objective is to optimize the film thickness of the light reflection film provided on the laser light absorption film, thereby absorbing the projected light with the laser light absorption film and reducing the heat capacity of the light reflection film. A light-scattering structure similar to that obtained using a high-output laser can be obtained using a laser, and high-speed writing with high contrast can be achieved.

[Effect]

By absorbing the projected light with the laser light absorption film and reducing the heat capacity of the light reflection film, the temperature of the glass substrate on the laser light absorption film side becomes higher than the temperature of the glass substrate on which the transparent electrode is provided, and the glass substrate on the transparent electrode side A temperature gradient is created between the glass substrate and the glass substrate on the laser beam side, and even with low-power semiconductor laser light, the heat generated in the light absorption film can be efficiently propagated to the liquid crystal, and the heat propagated to the liquid crystal can be released in a short time.

In addition, since there is a temperature gradient between the glass substrate on the transparent electrode side and the glass substrate on the laser light absorption film side, it is possible for the heat propagated to the liquid crystal to flow out to the glass substrate on the transparent electrode side in a short time, which causes light scattering. A writing state with strong characteristics can be obtained. In other words, a high-contrast display image can be obtained with high-speed writing.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to examples.

FIG. 3 is an explanatory diagram showing an embodiment of the multi-color projection type liquid crystal display device of the present invention. In the figure, reference numeral 21 denotes a projection light source, which is suitably a xenon lamp whose spectral distribution curve is in the wavelength range of visible light and has a continuous spectrum almost similar to that of sunlight. The projection light emitted from the projection light source 21 is filtered by a heat ray cut filter 22 to remove components in the ultraviolet wavelength range and heat rays in the near-infrared to infrared wavelength range, and converted into parallel light by the condenser lens 23. This parallel projected light is split into an S-polarized light component and a P-polarized light component by a polarizing beam splitter 24, and only the S-polarized light component is reflected toward the liquid crystal element 25, while the P-polarized light component is transmitted. Therefore, only the S-polarized light component with an amount of 1/2 of the incident projection light enters.
The light passes through the wave plate, is converted into circularly polarized light, and is irradiated onto the liquid crystal element 25.

Image information is written into the liquid crystal element 25 by this irradiation light by the laser 26, modulator 27, deflector 28, and liquid crystal drive circuit 29, and the pattern is reflected by the aluminum reflective film provided in the liquid crystal element, and then again. When passing through the input 74-wavelength plate 35, the circularly polarized light is converted into P-polarized light. The projected light, which has become a P-polarized component, passes through the polarizing beam splitter 24 with almost no loss, and passes through the projection lens 3o and the color filter 31.
As a result, a color image is displayed on the screen 32 after being colored and enlarged.

FIG. 1 shows the structure of a liquid crystal element used in this multicolor projection type liquid crystal display device, which is the key point of the present invention. As shown in the figure, the structure is such that a liquid crystal 6 is sandwiched between two glass substrates 2 and 8 having different heat capacities.

Glass substrate 2 contains chromium (900) and chromium oxide 8
A light absorption film 3 of 50 layers, a light reflection film 4 of Al, which is the key point of the present invention, and a liquid crystal alignment film 5 of organic matter and SiO are provided. Here, the lower limit of the film thickness of the Al light reflection film 4 is:
It is determined by the light reflection characteristics, and compared to the characteristics of a thicker film, the thickness at which the reflection characteristics do not deteriorate is 400.

On the other hand, on the glass substrate 8 on the projection light side, there is a liquid crystal alignment film 5 made of organic matter and SiO. A transparent electrode 7 made of Inz○3 is provided.

On the outside of these glass substrates 2 and 8, antireflection [1 and 9] is applied to suppress reflection of incident light.

The material of the glass substrate used in this example was soda glass, B
K-7, its thickness is 3+nm, 0.5mm. In addition, the wavelength of the semiconductor laser used in this implementation was 830 nm,
The projection light source is a xenon lamp.

In the liquid crystal element of this example, the heat capacity of the glass substrate on the projection side is about 10 times larger than that of the glass substrate on the laser beam side. Moreover, the thickness of the An light reflection film provided on the laser light absorption film is generally about 1000, but in this example, thermal analysis and reflection characteristics of the Al light reflection value including the laser light absorption film were performed. 400 people. With such a film configuration, the energy of the projected light can be absorbed by the laser light absorption film, and a temperature difference can be created between the glass substrate on the laser light side and the glass substrate on the projection light side.

In other words, the temperature of the glass substrate on the laser beam side is higher than that of the glass substrate on the projection light side, the heat generated in the laser light absorption film is efficiently propagated to the liquid crystal, and the heat applied to the liquid crystal layer is quickly absorbed by the projection light. It can be pulled out to the side glass board. As a result, the writing time is shortened, and a writing state with strong light scattering property is obtained, which improves the contrast.

In addition, by making the film thickness less than half of the conventional thickness by using the method of constructing the laser light absorption film and the light reflection film using Al, we not only improve the efficiency of heat propagation to the liquid crystal, but also reduce the heat capacity of the Al light reflection film. Therefore, the spread of heat caused by the laser beam can be reduced. In other words, the writing line width can be made thinner.

Improves accuracy.

The relationship between the film thickness of the Al light reflecting film, writing speed, contrast ratio, and writing line width is shown in FIGS. 4, 5, and 6. Further, FIG. 7 shows the relationship between the film thickness of the Al light reflecting film and the light reflectance.

FIG. 4 is a diagram showing the relationship between the film thickness of the Al light reflecting film and the writing speed, and is a ratio of the writing speed when the speed in the conventional device is set to 1.0. As shown in the figure, when the thickness of the AM light reflecting film is made thinner, the writing speed becomes faster, and when the film thickness is made thicker, the writing speed becomes slower. In this example, the lower limit of the film thickness of the Al light-reflecting film was set at 400 layers in consideration of the manufacturing precision of the Al light-reflecting film. We have confirmed that the thinner the thickness, the better.

FIG. 5 is a diagram showing the relationship between the thickness of the Al reflective film and the contrast ratio. As shown in the figure, compared to the conventional device,
The contrast ratio increases as the thickness of the l-light reflecting film decreases.

FIG. 6 is a diagram showing the relationship between the film thickness of the A0 reflective film and the writing line width. As shown in the figure, compared to the conventional device, Al
In the device of the present invention in which the thickness of the light-reflecting film is reduced, the writing line width is approximately 70%, and precision is improved.

Note that FIG. 7 is a diagram showing the relationship between the film thickness and reflectance of the A0 reflective film. The figure plots the values at a wavelength of 550 nm, and the reflectance is calculated when the thickness of the A0 reflective film is 40 nm.
It is almost constant in the range of 0 to 3000 people. Further, in the visible light wavelength range (400 to 700 nm), the spectral reflectance at a film thickness of 400 Å or more shows similar characteristics.

However, for less than 400 people, the spectral reflectance is somewhat different. Strictly speaking, even if the thickness of the A0 reflective film is around 380 people,
The characteristics are the same as those for 0 people, but the film deposition accuracy is ±50 nm with respect to the center wavelength. Therefore, also from the point of view of film deposition accuracy, it is appropriate that the lower limit of the film thickness of the Af1 reflective film is 400 people.

From the above, according to the present invention, it is possible to write images at high speed, and moreover, it is possible to display images of high spermatozoa with high contrast.

Furthermore, another embodiment that further improves the effects of the present invention is shown in FIG. As shown in the figure, the structure is such that a liquid crystal 6 is sandwiched between two glass substrates 2 and 8 having different heat capacities. The glass substrate 2 is provided with a heat insulating layer 10 made of SiO2 and an organic material, a light absorption film 3 made of chromium and chromium oxide, a light reflection film/electrode 4 made of aluminum, and a liquid crystal alignment film 5 made of an organic material and SiO. Here, the lower limit of the film thickness of the aluminum light-reflecting film/electrode 4 is determined from the light-reflecting characteristics and is approximately 400.

On the other hand, on the glass substrate 8 on the projection light side, a transparent electrode 7 of an organic material and a liquid crystal alignment film 5 of SiO, etc. 203 is provided.

On the outside of these glass substrates 2 and 8, antireflection films 1 and 9 are applied to suppress reflection of incident light.

The material of the glass substrate used in this example was soda glass, B
K-7, its thickness is 3nwn, 0.5mm. Furthermore, the wavelength of the semiconductor laser used in this example was 830 nm.
, the projection light source is a xenon lamp. In the liquid crystal element of this example, the heat capacity of the glass substrate on the projection side is approximately 15 times larger than that of the glass substrate on the laser beam side. Moreover, by providing a heat insulating layer under the light absorption film, it is possible to increase the temperature difference between the two substrates.

In other words, the temperature of the glass substrate on the laser light side is higher than that of the glass substrate on the projection light side, allowing the heat generated in the laser light absorption film to be efficiently propagated to the liquid crystal, and the heat added to the liquid crystal layer being projected in a short time. Pull it out to the optical side glass substrate. As a result, the writing time can be further shortened, and a written state with strong light scattering properties can be obtained, and the contrast can be improved.

〔Effect of the invention〕

As is clear from the above description, according to the projection device of the present invention, it is possible to improve the writing speed and contrast, which were problems with conventional projection devices using liquid crystals, and moreover,
Since the writing line width can be made thinner, there is an effect that high-speed writing and high-contrast, high-precision image display can be obtained.

[Brief explanation of drawings]

FIG. 1 is a structural diagram of a liquid crystal element used in the projection device of the present invention;
Fig. 2 is a structural diagram of a liquid crystal element used in a conventional projection device, Fig. 3 is a structural diagram of a color projection device embodying the present invention, and Fig. 4
The figure is a characteristic diagram showing the relationship between the film thickness of the liquid crystal element's Al light-reflecting film and the writing speed, Figure 5 is a characteristic diagram showing the relationship between the film thickness of the liquid crystal element's Al light-reflecting film and contrast ratio, and Figure 6 is a characteristic diagram showing the relationship between the film thickness of the liquid crystal element's Al light-reflecting film and the contrast ratio. FIG. 7 is a diagram showing the relationship between the Al light reflection value of the device and the writing line width, FIG. 7 is a diagram showing the relationship between the thickness of the A2 reflective film and the reflectance, and FIG. 8 is a diagram showing another example. 1.10...Laser light antireflection film, 2,8,11゜1
9...Glass substrate, 3,13...Laser light absorption film,
, 4.14...Light reflecting film and electrode, 5,16...
Liquid crystal alignment film, 6, 17... Liquid crystal, 7, 18... Transparent electrode, 9° 20... Visible light reflection prevention film, 13... Heat insulating layer, 15... Liquid crystal block film, 21.・・Light source, 2
2... Heat ray cut filter, 23... Condenser lens, 23... Polarizing beam splitter, 25... Liquid crystal element, 26... Laser, 27... Modulator, 28...
...Polarizer, 29...Liquid crystal drive circuit, 30...Projection lens, 31...Color filter, 32...Screen, 33...Beam splitter, 34...Mirror, 3
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Claims (1)

[Scope of Claims] 1. A laser beam generator, an optical means for two-dimensionally scanning the laser beam, and a liquid crystal element having a thermo-electro-optic effect; In a projection type liquid crystal display device in which an image is formed on a liquid crystal element using an optical means that scans dimensionally, and the image is enlarged and projected onto a screen, there is a space between two glass substrates constituting the liquid crystal element. A projection type liquid crystal display device characterized by being equipped with a means for creating a temperature difference. 2. A projection type liquid crystal display device according to claim 1, characterized in that, as a means for applying temperature between two glass substrates constituting a liquid crystal element, the heat capacities of the glass substrates are made different from each other. . 3. In claim 2, of the two glass substrates constituting the liquid crystal element, one with a small heat capacity is placed on the side where the laser beam is incident, and one with a large heat capacity is placed on the side where the projected light is incident. 1. A projection type liquid crystal display device characterized by having a structure in which: 4. In claim 3, of the two glass substrates constituting the liquid crystal element, the thickness of the light reflecting film/electrode made of Al provided on the glass substrate on the side into which the laser beam is incident is 4.
A projection type liquid crystal display device characterized in that the thickness is in the range of 00 to 1000 Å.